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andgabbana
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Consider the frictionless roller coaster shown:
http://i299.photobucket.com/albums/mm286/lanvin12/physics-2.jpg
If a 12 000-kg car starts at rest from Point A, calculate
a) the total energy of the system
b) the speed of the car at point B
c) the force that must be applied to bring it to a stop at point E
d) the work done to bring it to a stop at point EHere's what I did...
a)
E(T) = E(K) + E(P)
= 1/2(mv^2) + mgh
=1/2(12000 x 0) + (12000 x 9.8 x 95)
=1.1x10^7 J
b)
E(T1) = E(T2)
1/2(V1^2) + gh(1) = 1/2(v2^2) + gh(2)
9.8 x 95 = 1/2(v2^2) + (9.8 x 65)
931 = 1/2(v2^2) + 637
V(2) = 24m/s
c)
1/2(V1^2) + gh(1) = 1/2(v2^2) + gh(2)
9.8 x 95 = 1/2(v2^2) + (9.8 x 25)
V(2) = 37.04m/s
F = mass ([Vf^2 - Vi^2] / [2 x delta d])
= 12000 ([0^2 - 37.04^2] / [2 x 7])
=-3.2x10^4 J
d)
W=E(K)
=1.1x10^7 J
Do you see any mistakes?
http://i299.photobucket.com/albums/mm286/lanvin12/physics-2.jpg
If a 12 000-kg car starts at rest from Point A, calculate
a) the total energy of the system
b) the speed of the car at point B
c) the force that must be applied to bring it to a stop at point E
d) the work done to bring it to a stop at point EHere's what I did...
a)
E(T) = E(K) + E(P)
= 1/2(mv^2) + mgh
=1/2(12000 x 0) + (12000 x 9.8 x 95)
=1.1x10^7 J
b)
E(T1) = E(T2)
1/2(V1^2) + gh(1) = 1/2(v2^2) + gh(2)
9.8 x 95 = 1/2(v2^2) + (9.8 x 65)
931 = 1/2(v2^2) + 637
V(2) = 24m/s
c)
1/2(V1^2) + gh(1) = 1/2(v2^2) + gh(2)
9.8 x 95 = 1/2(v2^2) + (9.8 x 25)
V(2) = 37.04m/s
F = mass ([Vf^2 - Vi^2] / [2 x delta d])
= 12000 ([0^2 - 37.04^2] / [2 x 7])
=-3.2x10^4 J
d)
W=E(K)
=1.1x10^7 J
Do you see any mistakes?
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